Not even close. Off the top of my head Ultima Online, EverQuest,
as WoW is the longest running MMO to date
Interesting topic, and I think you might be right that the majority of people aren't really interested in a massively multi-player experience: they do want to be able to play with friends -- some of whom may be new friends met within the game -- and they want to have an audience they can show off their achievements to, but realistically they don't need thousands of concurrent players for that. This is perhaps an area where instanced content helps to reduce the crowding.
//Sorry, I've got more to say, but I'm currently on baby duty and she's started crying!